1. Field of the Invention
The invention relates to a rotary piston displacement machine for compressible media, having at least one delivery space which is delimited by spiral-shaped peripheral walls extending perpendicularly from a side wall of a fixed housing and leads from an inlet outside the spiral to an outlet inside the spiral, and having a spiral-shaped displacement body which projects into the delivery space and is mounted with respect to the delivery space so as to execute a rotary, twist-free movement and the center of which is offset eccentrically relative to the center of the peripheral walls in such a way that the displacement body at all times almost touches both the outer and the inner peripheral wall of the delivery space at in each case at least one advancing sealing line, and the spiral shape being selected so that the maximum theoretical inlet volume is achieved in the delivery space between displacement body and outer peripheral wall before the rotating rotor which carries the perpendicular displacement bodies assumes the 0.degree./360.degree. position relative to the delivery space, in which position the displacement body rests against the outer peripheral wall.
2. Discussion of Background
A rotary machine, the principle of which is known from DE-C3 26 03 462, is suitable for supercharging an internal combustion engine. It is distinguished by a virtually pulsation-free delivery of the working medium, which consists, for example of air or an air/fuel mixture. During the operation of a supercharger of this kind, a plurality of crescent-shaped working spaces are enclosed along the length of the delivery space between the displacer and the two peripheral walls of the delivery space, said working spaces moving through the delivery space from the inlet towards the outlet. In the process, their volume progressively decreases, with a corresponding increase in the pressure of the working medium.
A machine of the type mentioned at the outset is known from DE-A-3,138,585. The fact that the maximum theoretical inlet volume is greater than the actually achievable volume is a result of the fact that the spiral is composed of a plurality of mutually adjoining circular arc segments, each having a progressively smaller radius. A schematic diagram with regard to this behavior is illustrated in FIG. 2, which will be described later. In the known machine, the first time that the displacement body rests against the outer peripheral wall during the rotary movement of the rotor is in the so-called 0.degree./360.degree. position, at which point the intake procedure can be taken to be complete. However, tests using water models have shown that, given this configuration, a not inconsiderable part of the medium taken in flows back from the delivery space into the inlet during the closing procedure.